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Protective fish barrier constructed to keep Asian Carp contained in case of flooding was built in 2010 at a cost of $4.5 million. (Published Friday, June 13, 2014)

Updated at 10:53 AM CDT on Friday, Jun 13, 2014

A popular trail in suburban Cook County is disappearing under a mountain of dirt, along with sections of a barrier designed to prevent an invasive fish species from spreading.

Tens of thousands of cyclists enjoy Centennial Trail each year, according to Trails for Illinois. A miles-long stretch of the paved surface runs between the Des Plaines River and the Chicago Sanitary and Ship Canal near Willow Springs. The protective fish barrier, which was constructed to keep Asian Carp contained in case of flooding, was built in 2010 by the Army Corps of Engineers and runs along the Centennial Trail. The barrier cost taxpayers $4.5 million to erect.

Shedd: Keep Asian Carp out of Lake Michigan

Chris Coffey interviews experts from Shedd Aquarium about the importance of keeping the Asian carp invasive species out of Lake Michigan. (Published Wednesday, June 11, 2014)

A section of the trail between Willow Springs Road and Route 83 is temporarily closed while the Metropolitan Water Reclamation District of Greater Chicago (MWRD), the owner of the property, uses the location to construct a three mile-long hill that will be 60 feet high in some spots. MWRD is excavating a 10 billion gallon reservoir upstream of Willow Springs Road and as part of the process needs a place to put 1.8 million cubic yards of soil. The project is part of the larger Tunnel and Reservoir Plan (TARP), which the MWRD said will improve water quality and prevent flooding for the region.

Trail users are being diverted to the nearby John Husar I&M Canal Trail, which connects to Centennial Trail at Route 83.

But it has not been a smooth ride.

Critics said the I&M Trail is in poor shape and argue the MWRD surprised the public when it closed sections of the Centennial Trail last year.

"I think most people would be supportive, or are supportive, of their basements not flooding but MWRD was a little bit clumsy in telling people that the trail was going to be closed," said Steve Buchtel, executive director of Trails for Illinois.

Forest Preserves of Cook County, which manages Centennial Trail, said it was only notified about the hill construction after the project started. However, the lease allowed MWRD to close the trail.

MWRD told NBC 5 Investigates it was looking for other options until the last minute but ultimately decided to use its own nearby land for the hill construction. MWRD also said it held several public meetings regarding the trail closure and its plans for the hill.

However, some trail users point to the Asian Carp Barrier and wonder why it was even built only for sections of it to be buried nearly two years later. They claim it is a waste of taxpayer dollars to dump dirt on parts of the barrier and the paved Centennial Trail.

"It kind of disappoints me that we pay all these taxes and then we don't have the benefit of enjoying it," said cyclist John Zabinski.

The owner of a nearby bicycle repair shop claims the construction is impacting his business.

"Having those trails in a good state is not only better for business but better for everybody in the area," said 2 Bici Bike Shop owner Joe Gaspar.

MWRD said the construction of the hill will save taxpayers $10 million long-term. The dirt is being hauled just a few miles to the hill site and trucks are not using interstates to drive there.

"It is extremely convenient for the taxpayers that we are able to do that and build up a better barrier and accomplish that task really without charging the taxpayers any more money," said MWRD executive director David St. Pierre.

MWRD promises new mountain biking and hiking trails up the hill when it is completed in 2016.

Chicago Area Mountain Bikers (CAMBr) is a volunteer organization that promotes trail and free ride bicycling. The group's executive director said the hill construction on Centennial Trail is economically smart for taxpayers and should result in a better trail for biking.

Indeed, the Army Corps of Engineers told NBC 5 Investigates the hill should pose no problems in efforts to keep the Asian Carp from finding their way into new waterways.

Scientists at Shedd Aquarium said it is essential the Asian Carp do not ultimately wind up in Lake Michigan.

"They're just voracious eaters," said Roger Germann of Shedd Aquarium. "We want to make sure that that kind of devastation that we've seen on the Illinois River and other places doesn't happen in the Great Lakes, even though we're not quite sure what would happen, but why take that chance?"